ADR 0190: a seat's work is shared by its holders, and building is the first such role; design 18 says where a build runs

The build role was a mesh seat with one holder and its worker a push consumer with one delivery in
flight, so thirty-five images rebuilt serially on one machine while three others idled. The bus was
drawn for the alternative — a seat's accept subjects on a queue group of holders (design 25) — and
0190 uses it as one pattern for every role: a node seat with accepts, every holder pulling one ask
when idle, the asker addressing the role. Building is the first use: node-build-agent, held by the
build-agent module on every machine with a container runtime. Notes in 0121 and 0162 where their
facts went stale.

02-DECISIONS/README.md

@@ -188,6 +188,7 @@ python3 00-META/checks/index.py            fail if stale
 - **0185** — [A control plane behind its seat's row serves what it can](0185-a-control-plane-behind-its-seats-row-serves-what-it-can.md)
 - **0186** — [A ban list never holds a neighbour, and the mesh's own bans are its own wherever they hang](0186-a-ban-list-never-holds-a-neighbour.md)
 - **0187** — [A dead tracker is not the machine's failure](0187-a-dead-tracker-is-not-the-machines-failure.md)
+- **0190** — [A seat's work is shared by its holders, and building is the first such role](0190-a-seats-work-is-shared-by-its-holders-and-building-is-the-first-such-role.md)
 
 ### Its tiers, from the bottom up